Electronic Device

1. An electronic device comprising: a casing having an opening; a circuit board having a plurality of electrodes, the circuit board being provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, the contact member being provided so as to seal the opening; and a key unit having a key operation unit corresponding to the contact points, the key unit being provided to the opening; wherein the key unit is attached to the opening in an attachable and detachable manner, and the key unit includes: a plurality of press keys each having a flange on a back end, the press keys being provided to the key operation unit; a front-side frame having a front-side opening in which a tip end of each of the press keys is inserted, and a rib for securing a stroke when one of the press keys is pressed, the rib being provided around the front-side opening; and a back-side frame attached to the front-side frame from the back end side of the press keys, the back-side frame being configured to receive the back end of the press keys, and the back-side frame having a back-side opening in which a corresponding one of the contact points of the contact member is inserted in a manner contactable with the back end of a corresponding one of the press keys.

2. The electronic device according to claim 1 , further comprising a lock unit configured to fix the key unit to the casing.

3. The electronic device according to claim 2 , wherein the opening has a rectangular shape, the key unit has a frame having an approximately rectangular shape corresponding to the opening, and the lock unit is configured to hold down one side of the key unit so as to prevent the one side of the key unit from separating from the opening of the casing.

4. The electronic device according to claim 3 , wherein the lock unit is configured to slide in a direction orthogonal to the one side of the key unit.

5. The electronic device according to claim 4 , wherein: the key unit has a first engagement portion on the one side of the key unit, and the casing has a second engagement portion configured to engage with the first engagement portion, on an edge of the opening.

6. The electronic device according to claim 5 , wherein the lock unit is provided on a lower side of the opening of the casing.

7. The electronic device according to claim 1 , wherein the press keys include a number key and an operation key, and the electronic device is operable as an electronic calculator.

8. An electronic device comprising: a casing having an opening; a circuit board having a plurality of electrodes, the circuit board being provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, the contact member being provided so as to seal the opening; a key unit having a key operation unit corresponding to the contact points, the key unit being provided to the opening; and a lock unit configured to fix the key unit to the casing; wherein: the key unit is attached to the opening in an attachable and detachable manner, the key unit has a frame having a shape corresponding to a shape of the opening, and the lock unit is configured to hold down one side of the key unit so as to prevent the one side of the key unit from separating from the opening of the casing, the casing includes at least one hole formed on an edge of the opening at which the lock unit is provided, the hole having an edge for receiving an O ring, and the lock unit includes: an O ring arranged on the hole; and a lock cover configured to lock the key unit, the lock cover being arranged so as to cover the O ring and being movably screwed to the hole of the casing via a screw mounting portion inserted in the O ring.

9. The electronic device according to claim 8 , wherein: the casing includes a plurality of holes, the casing includes a recess formed in an intermediate portion between the holes formed on the edge of the opening, the lock unit includes a locking piece arranged in the recess, the locking piece includes a locking projection in an intermediate portion, and the lock cover includes a locking rib configured to be locked to the locking projection of the locking piece.

10. An electronic device comprising: a casing having an opening; a circuit board having a plurality of electrodes, the circuit board being provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, the contact member being provided so as to seal the opening; a key unit having a key operation unit corresponding to the contact points, the key unit being provided to the opening; and a packing member; wherein: the key unit is attached to the opening in an attachable and detachable manner, the casing includes a front-side casing having the opening, and a back-side casing to be joined with the front-side casing to constitute the casing, the front-side casing includes a groove formed around the opening, the contact member includes an outer peripheral rib which is insertable in the groove, the outer peripheral rib being formed around an outer periphery, the packing member is provided along outer peripheries of the front-side casing and the back-side casing and interposed between the front-side casing and the back-side casing, the front-side casing and the back-side casing include grooves into which the packing member is fitted, the grooves being formed along the outer peripheries, in portions of an upper side and a lower side of the casing, the packing member is exposed to be visible from an outside, in the front-side casing and the back-side casing, the grooves into which the packing member is fitted are formed in a plurality of layers at positions corresponding to the portions in which the packing member is exposed, and exposed portions of the packing member include a plurality of linear ribs corresponding to the grooves formed in the plurality of layers.

11. The electronic device according to claim 10 , wherein the outer peripheral rib is formed such that a tip end of the outer peripheral rib has a partial spherical shape in a sectional view and has a width larger than a width of a base end of the outer peripheral rib.

12. An electronic device comprising: a casing having an opening; a circuit board having a plurality of electrodes, the circuit board being provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, the contact member being provided so as to seal the opening; a key unit having a key operation unit corresponding to the contact points, the key unit being provided to the opening; and a lock unit configured to fix the key unit to the casing; wherein: the key unit is attached to the opening in an attachable and detachable manner, the key unit has a frame having a shape corresponding to a shape of the opening, and the lock unit is configured to hold down one side of the key unit so as to prevent the one side of the key unit from separating from the opening of the casing, the key unit includes: a plurality of press keys each having a flange on a back end, the press keys being provided to the key operation unit; a front-side frame having a front-side opening in which a tip end of each of the press keys is inserted, and a rib for securing a stroke when one of the press keys is pressed, the rib being provided around the front-side opening; and a back-side frame attached to the front-side frame from the back end side of the press keys, the back-side frame being configured to receive the back end of the press keys, and the back-side frame having a back-side opening in which a corresponding one of the contact points of the contact member is inserted in a manner contactable with the back end of a corresponding one of the press keys, the casing includes at least one hole formed on an edge of the opening at which the lock unit is provided, the hole having an edge for receiving an O ring, and the lock unit includes: an O ring arranged on the hole; and a lock cover configured to lock the key unit, the lock cover being arranged so as to cover the O ring and being movably screwed to the hole of the casing via a screw mounting portion inserted in the O ring.

13. An electronic device comprising: a casing having an opening; a circuit board having a plurality of electrodes, the circuit board being provided inside the casing; a contact member having a plurality of contact points corresponding to the electrodes, the contact member being provided so as to seal the opening; and a key unit having a key operation unit corresponding to the contact points, the key unit being provided to the opening; wherein: the key unit is attached to the opening in an attachable and detachable manner, and the key unit includes: a plurality of press keys each having a flange on a back end, the press keys being provided to the key operation unit; a front-side frame having a front-side opening in which a tip end of each of the press keys is inserted, and a rib for securing a stroke when one of the press keys is pressed, the rib being provided around the front-side opening; and a back-side frame attached to the front-side frame from the back end side of the press keys, the back-side frame being configured to receive the back end of the press keys, and the back-side frame having a back-side opening in which a corresponding one of the contact points of the contact member is inserted in a manner contactable with the back end of a corresponding one of the press keys, the casing includes a front-side casing having the opening, and a back-side casing to be joined with the front-side casing to constitute the casing, the front-side casing includes a groove formed around the opening, and the contact member includes an outer peripheral rib which is insertable in the groove, the outer peripheral rib being formed around an outer periphery.